I believe you’re approaching this from the wrong angle - this isn’t a tech problem, this is a people problem.
save them for posterity so that it lasts for periods like 200 years and more. This allows great-grandchildren and great-great-grandchildren to have access.
Instead of trying to get media that can last 200+ years, just teach your kids and grandkids the importance of keeping your family legacy alive. This will be way more effective than any medium you can come up it. Storage technologies change but the data remains the same, the future generations should be able to gradually upgrade storage mediums as necessary so the information keeps existing.